This invention relates to an improved vehicle headlamp comprising a concave parabolic enclosed reflector having internal reflective surfaces and a single filament light source of a tubular shape which cooperates with the reflector to develop forward illumination that is substantially devoid of uncontrolled light.
The present invention is primarily related to motor vehicle headlamps utilized to accommodate the aerodynamic styling of automobiles. In certain types of related headlamps, the geometry, such as the slope angle, is altered or reduced, relative to typical seal-beam headlamps, so that hood lines of the vehicle may be modified allowing contouring of the front end of the vehicle in order to reduce aerodynamically induced drag. Such headlamps are rectangular in shape and may incorporate relatively complex geometric parameters into the reflector and or lens of the headlamp for improving the optical performance of the headlamp which allows for modification of the styling of the vehicle while at the same time providing the frontward illumination needs of the vehicle. This improved reflector-lens combination is relatively expensive and as such becomes an integral part of the vehicle with its tungsten-halogen light source being of a replaceable type. While this rectangular automotive headlamp serves its desired function, it does present certain disadvantages primarily related to the cost of replacement. If such a headlamp, in particular the reflector or lens, becomes damaged because of a stone impact or by a related automotive collision, the owner of the automobile must, in certain cases, seek replacement from the automotive dealer of the particular brand of related automobiles rather than have the less expensive option of obtaining a replacement from retail outlets. In order to avoid such costly replacement cost, it is desired that a one-piece replaceable sealed beam headlamp be provided which satisfies the need for aerodynamic styling of automobiles.
The presently available conventional one-piece sealed beam rectangular headlamps, lacking in the geometry adaptable to allow contouring of the front end of the vehicle, and which comprise non-replaceable tungsten-halogen light sources have practical limits with regards to their frontal physical dimensions in order to provide at least the minimum frontward illumination requirements for the automobile. The limited dimensions relative to the frontal area of an automobile of currently available rectangular sealed beam headlamps which satisfy federal highway standards are 92 mm (height) by 150 mm (width). The dimension of the reflector and tungsten-halogen light source of these conventional headlamps are interrelated in that in order to provide the required illumination for the automobile, the light emitted by the light source must be efficiently intercepted and reflected by the reflector. The optical parameters (shape and geometric dimensions) of the reflector must be selected in accordance with the parameters of the light source (size and lumen output) so as to provide a beam pattern from the headlamp that is of a sufficient amount of directed light while at the same time limiting the amount of uncontrolled light. Additional practical reductions in the physical dimensions of the existing rectangular headlamp are primarily limited by the geometry of the filament, the bulb size and the material of the tungsten-halogen light source.
Current rectangular headlamps commonly utilize a tungsten-halogen light source that comprises a single-ended cylindrical envelope comprised of a glass material and lodging one or two filaments along with containing a halogen compound. The diameter, typically in the range of 10 to 15 mm, of the glass envelope must be of a selected and sufficient value so that during its operation it provides the desired housing to allow for the proper chemical reaction of its confined halogen compound, but at the same time to limit the operating temperature below the failure point of the glass envelope. If the operating temperature of the glass envelope is exceeded, the envelope will be damaged and thereby rendering the automotive headlamp inoperative. It is desired that the dimensions of the light source be reduced so that the dimensions of the conventional sealed beam rectangular headlamp may also be reduced. It is further desired that the characteristics of the envelope of the tungsten-halogen light source be improved so as to yield further reductions in the dimension of the reflector. Further, it is desired that the optical characteristics of the light source be improved so as to enhance the optical performance of the rectangular headlamp. Still further, it is desired that the efficacy or lumens/watt of the light source be improved so as to correspondingly improve the efficacy of the headlamp. It is desired that all of the improvements be accomplished so that the yielded rectangular headlamp having reduced physical dimensions and reduced power requirements provides the frontward illumination needs of the automobile.
Accordingly, it is an object of the present invention to provide a rectangular vehicle headlamp having reduced physical dimensions primarily yielded by a tungsten-halogen light source having reduced dimensions.
It is another object of the present invention to provide a tungsten-halogen light source having improved optical and operational characteristics along with reduced power requirements that contribute to enhancing the optical and operational characteristics of the rectangular headlamp.